tamerlan traveled to russia for six months last year. the fbi wants to know exactly who he saw and what he was doing, dan. >> let me get back to the fbi investigation into the older brother. you've been talking to the fbi all day. are they not expecting any sense of frustration or remorse over having missed what could have been a real opportunity here? >> they'll do a postmortem, which is normal in these cases, but they said they did what the lou and the constitution allows. >> pierre, thank you. >>> and in order to dig deeper into the lives of these two young suspects, we sent kirit radia to a rough and remote area where the family comes from. here is what he found today. >> reporter: in a tearful phone call with abc news this evening, the mother of the suspected boston bombers said she and her husband planned to travel to the u.s. to see their young son captured friday night. she insists her sons were set up, and that her eldest son was investigated because he loved islam and didn't do anything bad. her comments feed the mystery over w